The present invention is directed, in general, to audio and stereo systems and, more specifically, to a digital wireless premises audio system and method of operation thereof.
Film sound track, television audio and music playback formats used to be distinctly different products of industries usually working in isolation. In recent years, however, this has changed. The popularity of surround sound, especially in the home, has brought these industries and their audio formats closer together. Now, digital multichannel technology is fostering an even more consistent approach to sound reproduction. This technology eases the burden on both consumer and producer while providing greatly enhanced fidelity not only to the tonality of live sound but also to its spatiality.
Historically, the first commercially successfully multichannel sound formats were developed in the early 1950s for the cinema. Stereophonic sound (i.e., stereo) was a new concept to the public and was heavily promoted along with the new wide-screen formats. Stereo film sound tracks use a minimum of four channels, unlike a home stereo system which use only two channels. The use of two channels for the home was not due to listener preference or some predisposition on the part of the audio profession, but rather that the then-prevalent LP phonograph recording standard accommodated a left channel and a right audio channel.
Quadraphonic (i.e., quad) sound was an attempt to provide the home with a sound characteristic that more closely resembled a film theater. However, due to a variety of different formats and standards, the home quad sound system never became very popular. Around 1975, Dolby(copyright) Stereo was introduced into the film industry. Instead of being based on magnetic striping, it used an optical soundtrack technology similar to monophonic sound used in the 1930s. Dolby(copyright) Stereo enabled the film industry to encode two physical tracks on movie prints with four channels of information: left, center, right and surround (rear). This was accomplished using matrixing techniques.
Although Dolby(copyright) stereo provided an advancement in sound quality, it and all of its predecessors are based on analog audio techniques. In the late 1980s, Dolby introduced digital audio techniques. Dolby(copyright) Digital 5.1 Surround provides five discrete full-range channels (left, center, right, left surround and right surround) plus a sixth channel for powerful low-frequency effects having about 10 percent of the bandwidth of the other channels. All six digital channels offer the same high quality as contrasted to Dolby(copyright) Stereo wherein all channel quality was not equal.
The compact disc (CD) has afforded only incremental improvement over the best analog formats. However, the digital versatile disc (DVD), employing Dolby(copyright) Digital 5.1 Surround capability, provides multichannel surround sound and improved sound quality over the CD. The DVD is bringing about a true revolution in the way that music is reproduced and enjoyed, especially in the home. Home theaters now have source program material that is superior to any analog or previous digital formats, which causes other sources of sound distortion to surface.
Although DVD source program material is digital in format, speaker systems are still being driven by high power analog signals that are delivered through physical wires. To minimize distortion and attenuation, the physical wires are usually extremely large in diameter (gauge). If the wiring runs are long, even these large diameter wires may still cause unwanted distortions in sound quality. The long speaker wires may create adverse impedance matching situations for an amplifier/driver thereby affecting fidelity.
Another problem associated with home theaters is trying to run the speaker wires in existing structures where access is restricted. Multiple speaker group locations being supplied from one amplifier/driver location typically exacerbate this problem. Finally, there are structures where the wiring for surround sound speakers cannot be accommodated without extensive modification to the structure.
Accordingly, what is needed in the art is a way to implement an audio system that provides increased flexibility and reduces distortion.
To address the above-discussed deficiencies of the prior art, the present invention provides a digital wireless premises audio system, a method of operating the same and a home theater system incorporating the audio system or the method. In one embodiment, the audio system includes: (1) a digital audio encoder/transmitter, located on the premises, that accepts an audio channel in digital form, encodes the channel into a stream of digital data and wirelessly transmits the stream about the premises and (2) a speaker module, located on the premises, couplable to a power source and including, in series, a digital audio receiver/decoder, an audio amplifier and a speaker, that receives the stream, decodes the audio channel therefrom, converts the audio channel to analog form and employs power from the power source to amplify the audio channel and drive the speaker therewith.
xe2x80x9cPremisesxe2x80x9d is defined for purposes of the present invention as being a location. For example, xe2x80x9cpremisesxe2x80x9d may be one or more rooms in a building (such as a home) or a theater. Premises may also be any vehicle, such as a car, boat or airplane.
The present invention therefore introduces the broad concept (and resulting substantial utility) of (1) distributing the audio channels carried in an audio system in digital form to the speaker(s) to eliminate distortion that distribution of the audio channels over speaker cable in analog form would have caused and (2) transmitting the audio channels wirelessly to avoid the need for speaker cables (the digital form of the audio channels further serving to eliminate distortion that wireless distribution of analog audio channels would have caused).
In one embodiment of the present invention, the digital audio encoder/transmitter accepts a plurality of audio channels in digital form, encodes the plurality of channels into a stream of digital data and wirelessly transmits the stream about the premises, the system further including a plurality of speaker modules, located on the premises, that receives the stream and decode respective ones of the plurality of audio channels therefrom. Thus, the system may have only one channel and one or more speaker modules (typical of a public address system) or may have more than one channel and one or more speaker modules per channel (typical of a stereo, hi-fi or home theater system).
In one embodiment of the present invention, the power source is a line power source for the premises. In this embodiment, each speaker module may be plugged into a common wall outlet to derive the power required to amplify its audio channel. Alternatively, a power cable may couple the digital audio encoder/transmitter or another central source to each of the speaker modules (either in series or in parallel) to provide the necessary power.
In one embodiment of the present invention, the digital audio encoder/transmitter includes an analog to digital converter that generates the audio channel in digital form. Thus, the digital audio encoder/transmitter may be fitted with an analog-to-digital converter xe2x80x9cfront endxe2x80x9d to allow the encoder/transmitter to receive signals from conventional analog equipment, such as a compact disc (CD) player, audio cassette deck, video cassette recorder (VCR) or phonograph.
In one embodiment of the present invention, the speaker module further includes a channel selector, coupled to the digital audio receiver/decoder, that identifies an audio channel to be decoded from the stream. For example, a stereo may have channels xe2x80x9cAxe2x80x9d and xe2x80x9cB.xe2x80x9d In such system, the speaker modules may have channel selectors allowing them to reproduce sounds from either channel xe2x80x9cAxe2x80x9d or xe2x80x9cB,xe2x80x9d depending upon how a user may configure the channel selector. Those skilled in the art will understand the flexibility that this lends to a particular system, but will also understand that the present invention does not require this flexibility.
In one embodiment of the present invention, the stream conforms to a Bluetooth(trademark) standard. The Bluetooth(trademark) standard is set forth in xe2x80x9cBluetooth(trademark)xe2x80x94A Global Specification for Wireless Connectivityxe2x80x9d, which is available at html://www.bluetooth.com/developer/specification/specification.asp on the World Wide Web and is incorporated herein by reference.
In one embodiment of the present invention, the audio channel conforms to a standard selected from the group consisting of: (1) two-channel stereo, (2) four-channel quadraphonic, (3) Dolby(copyright) Stereo, (4) Dolby(copyright) Digital 5.1 Surround, (5) DTS(trademark) Surround 5.1 , (6) PAC Stereo Audio (commercially available from Lucent Technologies, Inc., Murray Hill, N.J.), and (7) MP-3 Stereo Audio. Those skilled in the pertinent art will understand that the systems and methods of the present invention are in no way limited to a particular protocol, format or configuration of channel or channel encoding.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.